Well screens having distributed flow

ABSTRACT

Well screens having distributed flow. A well screen includes a generally tubular structure having a longitudinal axis, and a passage for flow between an interior and an exterior of the well screen; and a filter assembly having a restriction to flow which varies in a direction parallel to the longitudinal axis. A well system includes a well screen including a passage for flow between an interior and an exterior of the well screen, and a filter assembly having a series of longitudinally extending sections, the series of filter assembly sections having a restriction to flow which increases in a direction toward the passage.

BACKGROUND

The present invention relates generally to equipment utilized andoperations performed in conjunction with a subterranean well and, in anembodiment described herein, more particularly provides well screenshaving distributed flow.

Conventional well screens have a filter or screen material whichoverlies one or more openings in a base pipe. The screen material has aconstant restriction to flow therethrough along its length. Due to thepresence of the openings, however, the pressure drop across the screenmaterial is greatest near the openings, and decreases away from theopenings.

As a result, higher flow rates and increased erosion are experienced inthe screen material near the openings where the pressure drop isgreatest. The remainder of the screen material is not effectivelyutilized.

Therefore, it may be seen that improvements are needed in the art ofconstructing well screens. It is among the objects of the presentinvention to provide such improvements.

SUMMARY

In carrying out the principles of the present invention, a well screenis provided which solves at least one problem in the art. One example isdescribed below in which flow through the well screen is distributed ina manner reducing localized erosion. Another example is described belowin which a filter assembly of the well screen has a restriction to flowwhich varies in order to more evenly longitudinally distribute flowthrough the filter assembly.

In one aspect of the invention, a well screen is provided which includesa longitudinal axis. A filter assembly of the well screen has arestriction to flow which increases in a direction parallel to thelongitudinal axis. The restriction to flow may increase in a directiontoward a passage for flow between an interior and an exterior of thewell screen.

In another aspect of the invention, a well system includes a well screenwith a passage for flow between an interior and an exterior of the wellscreen. A filter assembly of the well screen has a series oflongitudinally extending sections. The series of filter assemblysections have a restriction to flow which increases in a directiontoward the passage.

In yet another aspect of the invention, a well screen is provided whichincludes a tubular structure made up of multiple longitudinal tubularstructure sections and a filter assembly made up of multiplelongitudinal filter assembly sections. This construction of the wellscreen enables very long well screens to be assembled duringinstallation in a well.

These and other features, advantages, benefits and objects of thepresent invention will become apparent to one of ordinary skill in theart upon careful consideration of the detailed description ofrepresentative embodiments of the invention hereinbelow and theaccompanying drawings, in which similar elements are indicated in thevarious figures using the same reference numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic partially cross-sectional view of a well systemembodying principles of the present invention;

FIG. 2 is an enlarged scale schematic quarter-sectional view of a wellscreen which may be used in the well system of FIG. 1;

FIG. 3 is a schematic quarter-sectional view of a first alternateconstruction of the well screen;

FIG. 4 is a schematic quarter-sectional view of a second alternateconstruction of the well screen;

FIG. 5 is a schematic quarter-sectional view of a third alternateconstruction of the well screen;

FIG. 6 is a schematic quarter-sectional view of a fourth alternateconstruction of the well screen;

FIG. 7 is a schematic quarter-sectional view of a fifth alternateconstruction of the well screen;

FIG. 8 is a schematic quarter-sectional view of a sixth alternateconstruction of the well screen; and

FIG. 9 is a schematic quarter-sectional view of a seventh alternateconstruction of the well screen.

DETAILED DESCRIPTION

It is to be understood that the various embodiments of the presentinvention described herein may be utilized in various orientations, suchas inclined, inverted, horizontal, vertical, etc., and in variousconfigurations, without departing from the principles of the presentinvention. The embodiments are described merely as examples of usefulapplications of the principles of the invention, which is not limited toany specific details of these embodiments.

In the following description of the representative embodiments of theinvention, directional terms, such as “above”, “below”, “upper”,“lower”, etc., are used for convenience in referring to the accompanyingdrawings. In general, “above”, “upper”, “upward” and similar terms referto a direction toward the earth's surface along a wellbore, and “below”,“lower”, “downward” and similar terms refer to a direction away from theearth's surface along the wellbore.

Representatively illustrated in FIG. 1 is a well system 10 whichembodies principles of the present invention. A production tubing string12 is installed in a wellbore 14 of a well. The tubing string 12includes multiple well screens 16 positioned in an uncased generallyhorizontal portion of the wellbore 14.

One or more of the well screens 16 may be positioned in an isolatedportion of the wellbore 14, for example, between packers 18 set in thewellbore. In addition, or alternatively, many of the well screens 16could be positioned in a long, continuous portion of the wellbore 14,without packers isolating the wellbore between the screens.

Gravel packs could be provided about any or all of the well screens 16,if desired. A variety of additional well equipment (such as valves,sensors, pumps, control and actuation devices, etc.) could also beprovided in the well system 10.

It should be clearly understood that the well system 10 is merelyrepresentative of one well system in which the principles of theinvention may be beneficially utilized. However, the invention is notlimited in any manner to the details of the well system 10 describedherein. For example, the screens 16 could instead be positioned in acased and perforated portion of a wellbore, the screens could bepositioned in a generally vertical portion of a wellbore, the screenscould be used in an injection well, rather than in a production well,etc.

Referring additionally now to FIG. 2, an enlarged scale schematicquarter-sectional view of the screen 16 is representatively illustrated.The well screen 16 may be used in the well system 10, or it may be usedin any other well system in keeping with the principles of theinvention.

As depicted in FIG. 2, the well screen 16 includes a generally tubularstructure 20 and a filter assembly 22. The tubular structure 20 includesa member known to those skilled in the art as a base pipe 24. In theexample shown in FIG. 2, the base pipe 24 is provided with threaded endsfor interconnection in the tubing string 12. When interconnected in thetubing string 12, a longitudinal axis 28 of the tubular structure willform a part of the longitudinal axis of the tubing string.

A passage 26 is formed in the base pipe 24 in order to permit flowbetween the exterior and interior of the well screen 16. The passage 26is depicted in FIG. 2 as being positioned approximately in the middlealong the length of the base pipe 24, but other positions may be used,if desired. Furthermore, although only one passage 26 is illustrated,multiple passages may be used in keeping with the principles of theinvention.

The passage 26 may be formed directly through the base pipe 24 asdepicted in FIG. 2, or it may be formed in an orifice or nozzle, in acheck valve, in an inflow control device, in a locally or remotelyoperated valve or choke for selectively varying a rate of flow throughthe well screen 16, etc. Any type or configuration of the passage 26 maybe used in keeping with the principles of the invention.

In one of the important beneficial features of the well screen 16, thefilter assembly 22 is configured so that localized erosion of the filterassembly proximate the passage 26 is reduced or eliminated.Specifically, the filter assembly 22 includes a series of longitudinallyextending sections 30, 32, 34, 36, 38 having varying restrictions toflow therethrough, and which function to alter the distribution of flowthrough the filter assembly.

The section 34 which directly overlies the passage 26 is morerestrictive to flow than the sections 32, 36 which are on either side ofthe section 34. Similarly, the sections 32, 36 are each more restrictiveto flow than the sections 30, 38 on either side of the sections 32, 36.In this manner, the restriction to flow through the filter assembly 22increases in a direction toward the passage 26 and parallel to thelongitudinal axis 28 of the tubular structure 20.

The flow through the section 34 is indicated in FIG. 2 by a single arrow40, the flow through the sections 32, 36 is indicated by multiple arrows42, and the flow through the sections 30, 38 is indicated by a furtherincreased number of arrows 44. The increased number of arrows isintended to represent a reduced restriction to flow, and not necessarilyan increased flow rate through any section relative to another section.

For example, the restriction to flow through the sections 30, 32, 34,36, 38 may be designed so that the rates of the flows 40, 42, 44 areapproximately equal. In this manner, the flow through the filterassembly 22 may be evenly distributed along the filter assembly. Thisoption may be desired in order to evenly distribute erosion along thefilter assembly 22.

An alternative would be to design the flow restrictions through thesections 30, 32, 34, 36, 38 so that the flows 44 have an increased raterelative to the flows 42, and so that the flows 42 have an increasedrate relative to the flow 40. Yet another alternative would be to designthe flow restrictions so that the flow 40 has an increased rate relativeto the flows 42, and so that the flows 42 have an increased raterelative to the flows 44. Still another alternative would be to designthe flow restrictions so that the flows 42 have an increased ordecreased rate relative to each of the flows 44, 40. It will beappreciated that a wide variety of variations in flow rate may beaccomplished using the principles of the invention, which is not limitedto only the examples described above.

Each of the sections 30, 32, 34, 36, 38 is preferably made using aconstruction known to those skilled in the art as a “pre-pack,” in whichgranular material (such as sand, gravel, synthetic material, etc.) isformed in a layer (for example, using a resin to consolidate thegranular material) which acts to filter fluid flowing therethrough. Theresistance to flow through the sections 30, 32, 34, 36, 38 may be variedby changing the granular material type, changing the porosity and/orpermeability of the pre-pack layer, changing the size of particles ofthe granular material, changing the bonding resin or matrix, changingthe density of the granular material, changing the manner in which thegranular material is consolidated, changing the thickness of thesections, etc.

Of course, it is not necessary for the sections 30, 32, 34, 36, 38 to bemade using the pre-pack construction. The sections 30, 32, 34, 36, 38could instead be made using constructions known to those skilled in theart as “sintered,” “wire-wrapped,” “mesh,” “woven,” or any other type ofconstruction or combination of constructions. The sections 30, 32, 34,36, 38 may be joined to each other and to other components of the filterassembly 22 and tubular structure 20 using any method, such as welding,threading, bonding, fastening, etc.

Referring additionally now to FIG. 3, an alternate configuration of thewell screen 16 is schematically and representatively illustrated. Inthis configuration, the passage 26 is positioned closer to one end ofthe tubular structure 20 (the left end as viewed in FIG. 3), instead ofbeing positioned in the middle as depicted in FIG. 2.

Accordingly, the section 34 having the most restriction to flow ispositioned overlying the passage 26 on the left side of the filterassembly 22, the sections 32, 36 having reduced restriction to flow arepositioned to the right of the section 34, and the sections 30, 38having the least restriction to flow are positioned on the right side ofthe filter assembly. It will be appreciated that this configuration willresult in a more even distribution of flow through the filter assembly22, as compared to conventional well screen construction, since therestriction to flow still increases in a direction toward the passage26. Thus, it will also be appreciated that the passage 26 may bepositioned anywhere in the tubular structure 20 in keeping with theprinciples of the invention.

Referring additionally now to FIG. 4, another alternate configuration ofthe well screen 16 is schematically and representatively illustrated. Inthis configuration, the filter assembly 22 has the sections 30, 32, 34,36, 38 arranged longitudinally along the tubular structure 20 as in FIG.2, however, the sections are made up of layers of mesh screen material.

Specifically, the section 34 which overlies the passage 26 includesthree layers of mesh screen material, each of the sections 32, 36includes two layers of mesh screen material, and each of the sections30, 38 includes only one layer of mesh screen material. In this manner,the section 34 has an increased restriction to flow relative to thesections 32, 36, and the sections 32, 36 have an increased restrictionto flow relative to the sections 30, 38.

Other ways of varying restriction to flow using mesh material includechanging the mesh size, changing the mesh material, changing thematerial dimensions, changing the weave pattern, etc. Any way of varyingthe restriction to flow in the sections 30, 32, 34, 36, 38 may be usedin keeping with the principles of the invention.

Note that the layers of filter material in the sections 30, 32, 34, 36,38 are not necessarily made of screen mesh. For example, the layerscould instead be made of pre-pack, wire-wrapped, sintered, or any othertype of filter material, and any combination of filter materials.

The use of the layers of filter material results in the section 34 beingthicker than the sections 32, 36, and the sections 32, 36 being thickerthan the sections 30, 38. Differing thicknesses of filter material maybe used to vary restriction to flow through the sections 30, 32, 34, 36,38 without the use of multiple layers of filter material. For example,pre-pack, sintered and other types of filter material may be made indifferent thicknesses to thereby vary restriction to flow through thefilter material.

The filter assembly 22 as depicted in FIG. 4 also includes a protectiveouter shroud 46 overlying the sections 30, 32, 34, 36, 38. The shroud 46has openings 48 formed therethrough for admitting flow from the exteriorof the well screen 16.

Fewer openings 48 are provided for the section 34 as compared to thesections 32, 36, and fewer openings are provided for the sections 32, 36as compared to the sections 30, 38. It will be appreciated that areduced number of the openings 48 will result in an increasedrestriction to flow through the sections 30, 32, 34, 36, 38.Alternatively, or in addition, the openings 48 could have a reduced sizeto increase a restriction to flow therethrough. The openings 48 may beprogressively fewer and/or smaller for the sections 34, 32, 36, 30, 38to thereby produce increased restriction to flow through the sections.

Although the passage 26 is depicted in FIG. 4 as being centrally locatedin the tubular structure 20, it should be understood that the passagemay be otherwise positioned, and multiple passages may be provided, inkeeping with the principles of the invention.

Referring additionally now to FIG. 5, another alternate configuration ofthe well screen 16 is schematically and representatively illustrated. Inthis configuration, each of the sections 30, 32, 34, 36, 38 is made of amesh or woven filter material, but instead of using varying numbers oflayers to vary the restriction to flow through the sections, othercharacteristics of the material are changed.

For example, the section 34 may have a finer or denser weave as comparedto the sections 32, 36, thereby increasing the restriction to flowthrough the section 34. As described above, other characteristics of thefilter material may be changed to produce different restrictions to flowthrough any of the sections 30, 32, 34, 36, 38.

Another difference in the well screen 16 as depicted in FIG. 5 is thatthe shroud 46 has an even distribution of the openings 48. Thisarrangement of the openings 48 may be useful where a corresponding evendistribution of flow through the filter assembly 22 is desired.

Referring additionally now to FIG. 6, another alternate configuration ofthe well screen 16 is schematically and representatively illustrated.This configuration is similar in many respects to the configurationdepicted in FIG. 5, except that the passage 26 is positioned toward oneend of the tubular structure 20, and only three of the sections 30, 32,34 are used, with the most restrictive section 34 positioned overlyingthe passage.

Although three of the sections 30, 32, 34 are used in the configurationof FIG. 6, and five of the sections 30, 32, 34, 36, 38 are used in otherconfigurations described above, it should be understood that any numberof sections may be used in keeping with the principles of the invention.Furthermore, the sections 30, 32, 34, 36, 38 have been described aboveas providing a series of discrete increments in changing flowrestrictions, but it should be understood that the restriction to flowcould vary in a continuous manner between sections of the filterassembly, without departing from the principles of the invention.

Referring additionally now to FIG. 7, another alternate configuration ofthe well screen 16 is schematically and representatively illustrated. Inthis configuration, the filter assembly 22 has a restriction to flowwhich varies continuously along its length.

Specifically, the filter assembly 22 as depicted in FIG. 7 is made up ofa longitudinally distributed series of elements 50 which extendcircumferentially about the tubular structure 20. The filter assembly 22may be of the type known as “wire-wrapped,” in which case the elements50 may be triangular or trapezoidal shaped cross-section wire. Theelements 50 may be individual wraps of the wire, in which case theelements may be included in the same wire, or the elements could beseparately formed.

In the section 34 of the filter assembly 22 overlying the passage 26, aspacing S₁ between the elements 50 is relatively small (or even zero),thereby providing an increased resistance to flow through the section.In the section 32, the spacing S₂ between the elements 50 is increased,thereby providing a reduced resistance to flow as compared to thesection 34. In the section 30, the spacing S₃ between the elements 50 isfurther increased, thereby providing a reduced resistance to flow ascompared to the section 32.

It will be appreciated that the spacing between the elements 50 may bevaried in any manner along the length of the filter assembly 22 toproduce corresponding restrictions to flow and distributions of flowthrough the filter assembly. For example, the spacing between theelements 50 may be varied linearly, exponentially, or according to anyother function along the length of the filter assembly 22. The variedspacing between the elements 50 may be designed to produce an even oruneven distribution of flow through the filter assembly 22. The variedspacing between the elements 50 may be continuous or in discreteincrements. Thus, it should be understood that any manner of varying thespacing between the elements 50 may be used in keeping with theprinciples of the invention.

Although the passage 26 is depicted in FIG. 7 as being positioned towardone end of the tubular structure 20, the passage may be otherwisepositioned, and any number of passages may be provided. If, for example,the passage 26 is positioned at a middle of the tubular structure 20,the spacing between the elements 50 could decrease progressively fromeach end of the filter assembly 22 toward the middle. Thus, it is notnecessary for the spacing between the elements 50 to only increase ordecrease in a certain direction in the filter assembly 22.

Referring additionally now to FIG. 8, another alternate configuration ofthe well screen 16 is schematically and representatively illustrated. Inthis configuration, a device 52 of the type known to those skilled inthe art as an “inflow control device” is used to restrict the flow offluid into the interior of the tubular structure 20 after the fluid hasflowed through the filter assembly 22.

Many different types of inflow control devices are available. The device52 includes multiple nozzles or orifices 54 in communication with achamber 56 at one end of the filter assembly 22. Thus, the passage 26extends through the orifices 54 and the chamber 56.

Other types of inflow control devices include helical or otherwiselabyrinthine passages, tubes, etc. Any type of inflow control device maybe used for the device 52 in keeping with the principles of theinvention.

Note that, in this configuration of the well screen 16, the filteringportion of the filter assembly 22 does not directly overlie the passage26. Nevertheless, the filter assembly 22 may still have a restriction toflow which increases in a direction toward the passage 26, for example,to reduce erosion of the elements 50 adjacent the device 52.

Referring additionally now to FIG. 9, another alternate configuration ofthe well screen 16 is schematically and representatively illustrated. Inthis configuration, the tubular structure 20 and the filter assembly 22are each made up of multiple longitudinal sections which allow very longlengths of the well screen to be assembled during installation in awell.

The various sections of the tubular structure 20 are preferably attachedto each other using flush threaded joints 58. The flush joints 58 areconveniently joined during installation using conventional rigequipment, and the joints conserve radial space in the well screen 16.

The various sections of the filter assembly 22 are also preferablyattached to each other using flush threaded joints 60. The flush joints60 provide for convenient arrangement of the sections of the filterassembly 22, so that the distribution of flow restriction along thefilter assembly may be changed as desired. Alternatively, otherattachment methods (such as welding, bonding, fastening, etc.) may beused for the joints 58, 60, if desired.

Of course, a person skilled in the art would, upon a carefulconsideration of the above description of representative embodiments ofthe invention, readily appreciate that many modifications, additions,substitutions, deletions, and other changes may be made to thesespecific embodiments, and such changes are within the scope of theprinciples of the present invention. Accordingly, the foregoing detaileddescription is to be clearly understood as being given by way ofillustration and example only, the spirit and scope of the presentinvention being limited solely by the appended claims and theirequivalents.

1. A well screen, comprising: a longitudinal axis; and a filter assemblyhaving a restriction to flow which varies in a direction parallel to thelongitudinal axis.
 2. The well screen of claim 1, further comprising apassage for flow between an interior and an exterior of the well screen,and wherein the restriction to flow increases in the direction towardthe passage.
 3. The well screen of claim 1, wherein the restriction toflow varies in discrete increments.
 4. The well screen of claim 1,wherein the restriction to flow varies continuously.
 5. The well screenof claim 1, wherein the varied restriction to flow results from avariation in a filter material of the filter assembly, and where thevariation is in at least one of density, permeability, porosity, bondingresin, matrix, thickness, particle size, consolidation, and materialtype of the filter material.
 6. The well screen of claim 1, wherein thevaried restriction to flow is a result of a varied number of layers offilter material in the filter assembly.
 7. The well screen of claim 1,wherein the varied restriction to flow is a result of a varied number ofopenings in the filter assembly.
 8. The well screen of claim 1, whereinthe varied restriction to flow is a result of a varied size of openingsin the filter assembly.
 9. The well screen of claim 1, wherein thevaried restriction to flow is a result of a varied spacing betweensuccessive elements of the filter assembly.
 10. The well screen of claim1, wherein the passage extends through a device which restricts flow ofa fluid which flows through the filter assembly.
 11. A well system,comprising: a well screen including a passage for flow between aninterior and an exterior of the well screen, and a filter assemblyhaving a series of longitudinally extending sections, the series offilter assembly sections having a restriction to flow which increases ina direction toward the passage.
 12. The well system of claim 11, whereina first one of the sections overlies the passage, and a second one ofthe sections is farther from the passage than the first section, therestriction to flow through the first section being greater than therestriction to flow through the second section.
 13. The well system ofclaim 11, wherein the restriction to flow varies in discrete increments.14. The well system of claim 11, wherein the restriction to flow variescontinuously in the series of sections.
 15. The well system of claim 11,wherein the increased restriction to flow results from a variation in afilter material of the filter assembly, and where the variation is in atleast one of density, permeability, porosity, bonding resin, matrix,thickness, particle size, consolidation, and material type of the filtermaterial.
 16. The well system of claim 11, wherein the increasedrestriction to flow is a result of an increased number of layers offilter material in the filter assembly.
 17. The well system of claim 11,wherein the increased restriction to flow is a result of a decreasednumber of openings in the filter assembly.
 18. The well system of claim11, wherein the increased restriction to flow is a result of a decreasedsize of openings in the filter assembly.
 19. The well system of claim11, wherein the increased restriction to flow is a result of a decreasedspacing between successive elements of the filter assembly.
 20. The wellsystem of claim 11, wherein the passage extends through a device whichrestricts flow of a fluid which flows through the filter assembly.
 21. Awell screen, comprising: a tubular structure made up of multiplelongitudinal tubular structure sections; and a filter assembly made upof multiple longitudinal filter assembly sections.
 22. The well screenof claim 21, further comprising a passage for flow between an interiorand an exterior of the well screen, and wherein the filter assemblysections have a restriction to flow which increases in a directiontoward the passage.
 23. The well screen of claim 21, wherein the tubularstructure has a longitudinal axis, and wherein the filter assembly has arestriction to flow which varies in a direction parallel to thelongitudinal axis.
 24. The well screen of claim 21, wherein the tubularstructure sections are joined to each other with flush threaded joints.25. The well screen of claim 21, wherein the filter assembly sectionsare joined to each other with flush threaded joints.